Sealing plugs



INVENTOR s ATTORNEY .April 20, 1965 N. BRADLEY ETAL SEALING PLUGS Filed Feb. 19, 1960 United States Patent O 3,179,279 SEALING PLUGS Norman Bradley, Culcheth, Warrington, and .lack Jones,

Manchester, England, asisgnors to United Kingdom Atomic Energy Authority, London, England Y Filed Feb. 19, 1960, Ser. No. 9,847 Claims priority, application Gre'at Britain, Mar. 11, 1959,

2 Claims. (Cl. 2241-245) This invention relates to sealing plugs and has one application to .the sealing of stand-pipes providing access to the core of a steam cooled or steam generating nuclear reactor.

A nuclear reactor which is part of a sys-tem for generating electricity on a commercial scale is preferably provided -With means for lrefuelling the reactor without shutting d-own .the reactor (generally referred to as ou-loa refuell-ing). To this end the react-or is provided with a series off stand-pipes giving access to the core of the reactor, the pipes being sealed during normal reactor operation and ope-n to a refuelling machine during a -refuell-ing operation. The sealing arrangements for the standapipes have to meet an onerous specification. iF or example, in a steam cooled or steam generating reactor the sealing arrangements may have to operate at 80() psi, pressure, 260 C. temperature whilst being leak free (as :the steam would be activated in its passing through .the core) and readily removable, storable and replaceable by remotely operated tools.

Accord-ing .to the invention, a sealing plug comprises a plug body, means defining an annular projection about .the periphery Ithereof, a coaxial sleeve member located by and movable relative .to the body, at least one pipe sealing ring .of resilient material disposed between the annular projection and the sleeve member, means including a spring component .tending to urge the sleeve member and the body member together so .as to compress the ring, a weight member heavy enough to overcome the urging etl'ect of the spring component connected to said spring component and depending from the body, and Where-in the interior of a pipe is provided with supp-ort means for supporting .the weight of said weight member to allow said spring component to take effect.

A sealing plug according to the invention will now be described by way of example with reference to the accompanying drawings in which iFIG. Il is a sectional elevation of a stand-pipe associated with a steam-cooled nuclear reactor and FIG. 2 is an enlarged view of the part ot FIG. 1 enclosed by the lbox IVI.

In FIG. 1 there is shown, partly diagrammaft-ically, a core 1 of a water-moderated steam-cooled nuclear reactor having a bottom reflector 2 and a top retlector 3. Above .the reector 6 there is provided a neutron shield 4 followed, in the upward direction, by a void 5 in which reactor coolant pipes' are accommodated. and a gamma shield 6. The components 1-6 referred to above are penetrated by a pipe system which consists (starting at the bottom) of a zirconium pressure tube 7, a joint 8, a steel pipe 9, having a steam inlet connection 10, and, at the top, a stand pipe A1'1 having a connection 12 with a branch 7-1 leading to the atmosphere and a branch 72 leading to a condenser 73. The llnariches 7d, 72 have shut-olf valves 74, 7:5 respectively. Under normal operating conditions, valve 75 is open and valve 74 closed. The stand pipe 11 is equipped with two sealing plugs 118, =14; one below and one above the connection 1,2. The plug -1-3 carries a gamma shield plug 15 maintaining the integrity of the shield 6.

Sealing plugs I1-3 and |14 will now be described in detail with reference to FIG. 2. It will be appreciated 14 forms no part of the claimed invention.

The plug 13 has two parts; a sealing part -16 and a latch 3,179,279 Patented Apr. 20, 1965 ICC part 17. The sealing part has a resilient chevron packing made from a number of chevron lrings 1-8 of asbestos impregnated with silicone rubber, .the rings being expansible radially .to effect a seal by axial loading provided by a spring d'9 act-ing on a plug body 20 having an annular projection a about its periphery. The rings 18 are disposed between the projection 20a and a coaxial sleeve part 2-2 located by and movable relative thereto .the plug body 23. The sleeve part 22 which presses on :the rings 18, is part of a cap-like compone-nt 21 having apertures 66 in its base'. The loading of the spring |19 is transmitted to the body 2? by contact at the lower end of the spring with an end plate 27 secured with screws 28 and is transmitted to the component 21 by way of an endcap 23 connected with a rod 24 having a thread 25 and nut and washer .26. The rod 24 passes through a hole 29 in the plate l27. The thread 25 also connects with a flange l secured .t-o :the shield plug k15 by bolts 3K1.

The latch part has a ring of balls -32 supported in a cage 33 and in contact with the member 20. The ring of balls 32 can be expanded `radially Ito latch in a circumferential recess 34 in .the stand pipe -1l1 by a conical-shaped ball displacing member 35. The member 35 is provided with a lifting hook 36 and the body 20 has a lifting bolt 37 .terminating in a nut and washer 38 in a cavity 65 in the conical part 35.

`In the operation of sealing and latching of the plug 13, the spring .119 creates sufiicient pressure at the rings 1-8 to effect a preliminary seal. Subsequently, when the reactor is pressurised, full reactor pressure (800 p.s.i.) leaking past the shield plug acts on the rings 18 to lincrease their seal-ing effec-t against reaction oiered by the body 2t).

` The reactor pressure also acts, through the apertures 66 in the component 21, on the body 20 and the resultant Vforces are transmitted to the balls 32.

The plug 14 also has two parts; a sealing part 39 and a latch part 40. The sealing part has a chevron packing ma-de from a number of chevron rings 41 radially expansible by axial force applied by a nut and screw 42. (These.

rings 41 do not have such an arduous duty to perform as corresponding rings d'8 in plug 13 and could therefore be .of other construction.) The nut is the boss of a ring 43 having a sleeve 44 which presses against l[he rings 41. The screw is the lower threaded part of a rod 45 having a flange 46 movable in a cavity 47 .and limited in its axial movement by a st-op plate 48 held by screws 49. The ring 43 is prevented from rotating by a pin 64. Near the upper end of the rod 45 there is a thread 50 and a bush 51. T he thread 50 carries a pair of lock-nuts 5-2 which are located in a cavity 53 closed by a stop-plate 54 secured by screws 55. The upper end of the rod 45 has iixed to it a toothed wheel 56 and .the rod 51 is termi nated in a lifting hook 57. The compression force provide-d by the nut land screw [to the rings 41 .acts against a member 5S.

The latch .part 4t) has a ring of balls 59 supported in a cage 60 and the .balls are in contact with the member 58. The ring ot balls -59 can be expanded radially to latch in a circumferential recess 611 in the stand pipe 11 under axial loading provided by the member 58 in combination -with a conical shaped .part 62. The top end of the part 62 is provided with splines 63.

In the operation of sealing and latching of the plug 14 the plug is inserted into the stand-pipe 11 by suspension from .the hook 57 with the nut and screw 42 released s0 that .the rings 411 are not compressed andthe balls 59 are in their innermost position, the rings 41 and member SS having lowered themselves with the nut and screw released. The nut and screw are now .tightened up (by a tool causing relative rotation between splines 63 and toothed Wheel 56) so that rings 441, member 58 and balls 59 are elevated. The .balls are driven int-o tight engagement between the conical shaped par-t y62 and recess 6l and the rings il are compressed to make a seal.

To unplug thepstand pipe to .all-ow fue-l elements to be inserted and withdrawn a fuel element -refuelling machine is joined ywith the stand-pipe 1li and a remotely operated tool in .the refuelling machine is advanced to engage with splines e3 and wheel 56 of plug 14. The pipe 12 is disconnected fnorn Vists condenser and opened to atmosphere by closing valve 755 and opening valve 74. That part of 4the tool engaging with wheel S6 is rotated .to release the compression lot rings 41 and balls 59 and the plug 14 removed by liiiting on the hook 57.

The valves 74, 75 (QFG. 1) are now closed and the stand pipe steam-pressurised. On balancing pressure across plug 1:3 the loading on tire chevron rings 1S is re- .duced 'to that atiorded by the spr-ing 1 9. Lifting on the hook 36 allows Ithe balls to be released and the conicalshaped member 35 contacts the nut 38.' The lift is then applied also to the body 2@ via the nut 38 so that the spring compresses under the weight of the plug 15. The component 2d remains stationary with the plug 15 whilst the spring compresses, thus releasing the loading on the rings '18 so that the sealing of the rings 1S is broken. Further lifting then removes the .plug 1S so providing access' to `the fuel elements. v

The provision of the two plugs 1:3, `14 with the connection :12 between them to `a condenser ensures that any leakage past plug 13 (which may be contaminated with radioactive material) is removed to the condenser.- It also provides an interspace `from which the integrity of the sealing of the plug 13 can be examined -by flow measurement -in the .pipe y12 and the provision of two Vplugs also provides security if the plugl should fail :to seal. The plug i4, whilst lnormally subject to atmospheric pressure acting inwards is nevertheless capable .of withstanding full reactor pressure `of I800 p.s.i. acting outwards. The plug 13 is self ysealing when subjected to reactor pressure. `This greatly facilitates manipulation, The self sealing is operated by the spring 1.9 in conjunction with the weight of the shield plug d5. When the plug ,13 is being inserted the weight of the shield plug overcomes the tension in the spring T19 so that the chevron packing 1S is loose. Willen the plug yll5 -i-s arrested Iby a seating lilla in the bore of the stand-.pipe ylill the tension in the spring 19 compresses the packing-.18 to make an initial seal which is finally made on the application `of reactor pressure.

We claim: y

1. iln the combination vof an upright pipe, a plug for sealing the bore of the pipe and pipe-engaging latch members carried by .the plug vfor receiving the plug in the bore of the pipe, the improvement wherein the plug comprises a plug body,l means deining an annular projection about the periphery thereof, la coaxial sleeve member located by .and movable relative to the body, atleast one pipe sea'ling ring of `resilient material disposed between the annular projection land the sleeve member, means including a spring-component .tending to urge .the sleeve member and the body member together so as to compress the ring, a .weight member heavy enough to overcome the urging etect of the spring component, connected to said spring component and depending from `the body and wherein the interior of the pipe is provided with support component fior supporting the weight of said weight member and `thereby allowing said spring component to urge said sleeve mem-beragainst said ring as aforesaid. f

2. In .the combinati-on of claim 1, the further improvernenit wherein the pipe-engaging latch members comprise a plurality of balls disposed radially about the plug body, in combination with .a gnavity-operated member defining inclined surfaces adapted to displace said balls outwardly from ythe body.

References VCited by the Examiner UNETEB STATES kPATENTS 491,184 2/93 McCartney V220--245 1,185,116 5//16 Mack 22S-24.5 .2,298,552 10/42 Du Vall 220-24-.5 2,409,811 10/46 Taylor et al. 16e-125 :2,475,748 7/ 49 Le Roy 2GO-24-5 2,538,288 1/5i1 Whitsel 220*24.5 2,848,404 8/.58 Treshow 204-193-39 2,851,410 y9/58 Vernon et al. 204-15439 2,893,693 7/59 Clark 166-136 X n FOREIGN PATENTS 556,839 6/ 5 S Italy.

806,984 1/ 59 Great Britain.

CHARLES OCONNELL, Primary Exalrzner.

R. L. CAMPBELL, L. D. ROSDAL, Examiners. 

1. IN THE COMBINATION OF AN UPRIGHT PIPE, A PLUG FOR SEALING THE BORE OF THE PIPE AND PIPE-ENGAGING LATCH MEMBERS CARRIED BY THE PLUG FOR RECEIVING THE PLUG IN THE BORE OF THE PIPE, THE IMPROVEMENT WHEREIN THE PLUG COMPRISES A PLUG BODY, MEANS DEFINING AN ANNULAR PROJECTION ABOUT THE PERIPHERY THEREOF, A COAXIAL SLEEVE MEMBER LOCATED BY AND MOVABLE RELATIVE TO THE BODY, AT LEAST ONE PIPE SEALING RING OF RESILIENT MATERIAL DISPOSED BETWEEN THE ANNULAR PROJECTION AND THE SLEEVE MEMBER, MEANS INCLUDING A SPRING-COMPONENT TENDING TO URGE THE SLEEVE MEMBER AND THE BODY MEMBER TOGETHER SO AS TO COMPRESS THE RING, A WEIGHT MEMBER HEAVY ENOUGH TO OVERCOME THE URGING EFFECT OF THE SPRING COMPONENT, CONNECTED TO SAID SPRING COMPONENT AND DEPENDING FROM THE BODY AND WHEREIN THE INTERIOR OF THE PIPE IS PROVIDED WITH SUPPORT COMPONENT FOR SUPPORTING THE WEIGHT OF SAID WEIGHT MEMBER AND THEREBY ALLOWING SAID SPRING COMPONENT TO URGE SAID SLEEVE MEMBER AGAINST SAID RING AS AFORESAID. 